How to add months to date field in salesforce using formula expression builder

If you want to add say 6 months to the date fields in salesforce,its not straightforward. Please see this example as to how to achieve it.

DATE( 

YEAR(start_date__c) + FLOOR( ( MONTH (start_date__c) + 6 - 1 ) / 12 ), 

MOD( MONTH (start_date__c) + 6- 1 + 

IF( DAY (start_date__c) > CASE( MOD( MONTH(start_date__c) +6- 1, 12 ) + 1, 

2, 28, 

4, 30, 

6, 30, 

9, 30, 

11, 30, 

31 ), 1, 0 ), 12 ) + 1, 

IF( DAY(start_date__c ) > CASE( MOD( MONTH(start_date__c ) +6 - 1, 12 ) + 1, 

2, 28, 

4, 30, 

6, 30, 

9, 30, 

11, 30, 

31 ), 

1, DAY(start_date__c ) 

) 

)